Electric water heater



1952 D. M. MGGINNIS 2,523,153-

ELECTRIC WATER HEATER Filed Nov. 4, 1950 5 Sheets-Sheet 1 Paragon HEAYOHHEATON ZSnventor,

Gttomeg Dec. 23, 1952 McG|NN| 2,623,153

ELECTRIC WATERHEATER Filed Nov. 4, 1950 5 Sheets-Sheet 2 II'I,

Gttorneg 1366- 23, 1952 D. M. M GINNIS ELECTRIC WATER HEATER 5Sheets-Sheet 3 Filed Nov. 4, 1950 3rmentor, llY/Y/S 94140 M M fiGttorneg Dec. 23, 1952 D. M. M GINNIS 2,623,153

' ELECTRIC WATER HEATER Filed Nov. 4, 1950 5 Sheets-Sheet 4 95 f. FUSESnventog "$330.2 $5353 DA V/D A7 /'7 @mw/s ttorneg Dec. 23, 1952 o;M.-MIGINNI SW 2,

[ELECTRIC WATER HEATER Filed Nov. 4, 1950 5 Sheets-Sheet 5 3noentor,

(Ittomeg Patented Dec. 23, 1952 UNITED STATES PATENT OFFICE- Y 2,623,153ELECTRIC ATER HEATER David M. McGinnis, Los Angele's, Calif. ApplicationNovember 4, 1950, Serial No. 194,113

4 Claims. 1

This invention relates to apparatus for electrically heating fluids andparticularly to e1ectrically heated steam generators.

A great number of industries utilize steam gen laundries, and forheating and air conditioning .in hotels, restaurants and businessbuildings.

The personnel making use of steam generators in industries, such asmentioned, are generally untrained mechanically, and it is, therefore,very desirable to provide steam generators so designed that they willoperate automatically with little more manipulation than pushing startand stop push buttons.

While electrically heated steam generators have been provided previouslybecause of their advantages in some respects, such as the absence offlame and consequent danger of explosion and of water tubes with theirneed of periodical cleaning and other advantageous features, they havenot come into wide use to the best of my knowledge because of variousdisadvantages.

Electrically heated steam generators at present in use are often ofcomplicated, bulky and inefficient design, in part due to want of properunderstanding and faulty application of correct principles. Suchprevious installations were consequently expensive both in first costand in maintenance and required the frequent attention of skilledpersonnel. Such installations were also generally slow in generatingsteam both in starting and recovering loss of pressure.

It is an object of this invention to provide a compact electricallyheated steam generator so arranged that steam at the generally requiredpressure of 100 lbs. per square inch, for instance, is generated fromcold water in less than five minutes, and loss of pressure due toaverage use is made up in a matter of seconds.

It is a further object of the invention to provide a completeelectrically heated steam generating plant arranged in a single casingso that it may be set up for use merely by connecting water and powerlines to'the casing.

Another object of the invention is to provide a complete electricalsteam generator plant in a single compact casing which may be shippedassembled, wired and ready for use, yet which is so arranged that allcomponent parts may be readily inspected or serviced. A still furtherobject of my invention is to pro- ..pletely assembled condition;

2 vide an electrically heated steam generator fitted with controlsproviding an automatically operated plant requiring no othermanipulation than the'operation of simple start and "stop control means.

Another objectqf my invention is to. provide heating elements foranelectric steam generating plant, said elementsjjbeing so constructed andarranged that exceptionally. fast. steamgeneration is provided both inraisingsteam andrecovering steam pressure lost due'to use of the steam.

A further object of my invention is to provide a steam generator inwhich the boiler, shelljjis arranged in a heat insulated compartment.and is surrounded by a dead air space, the boiler being uninsulatedwherebyit may be inspected by removing the top of the compartment.

Still further objects .and vfeaturesof. the invention will appear fromthe followingdescription .read with reference to the accompanyingdrawings, which illustrate one embodiment of the in;-

vention, at present considered preferableby .me.

Figure 2 is a side elevation looking in the direction of the arrow 2 inFigure l, but with partof the exterior casing of the steamgenerator-broken away and showing some interior parts in section andothers unsectioned.

Figure 3 is a vertical cross-section on-the line 3-3 of Figuref2; IFigure 4 is a horizontal cross-:sectiononthfe line 44 of Figure 2;

Figure 5 is an enlarged detail view of the heating elements mounted on acommon base plate disassembled from the heater; and" Figure 6 is aschematic. diagram showing-the electrical circuit for the'electricallyoperated components of the steam generator.

- In the drawings, the numeral I0 indicates the outer casing of thesteam generator which-is divided by a partition H, as clearly shown inFigure 3, into a smaller lower compartment l2, and a larger uppercompartment l3.

In the lower compartment, -apiston-type water pump i4 is positioned. Thepump is driven by electric motor l5 and a belt Hi mounted on the motorbelt pulley I1 and pump belt pulley Ill. The pump and motor form anassembly mounted on the base panel l9, which is supported above thefloor 20 on a frame 2i of any suitable con struction.

The front of the lower compartment is fitted with a large door 22(Figure 1) enabling ready access to be had to the pump which is fittedin the front portion of the lower compartment. A water storage tank 23is fitted in the rear portion of the lower compartment. Boiler feedWater is admitted to the tank and maintained at a constant level thereinby a valve 24 operated by a float and lever 25 which controls the inletof water from water supply pipe 26, through feed valve 26V.

Waterfrom the tank is drawn by the pump through a strainer 21 in thetank and a shutoff cock 28 between the tank and the pump, which permitsthe pump to be removed for any reason without requiring the tank to beemptied.

The pump discharge is controlled by acheck valve 29 and a stop valve 30asrequiredbysteam boiler regulations.

The boiler is formed as a shell 3| serving as a combined water and steamchamber U-shaped inacrosssection, the top ofthe boilershell being closedby aremovablymounted flat plate, 32. The rounded, bottom of the shell issupported on a. cylindrical ,supportingflange 33 bolted to thehorizontal partition II and welded around the bottom portion of theshell. The heating elements indicated generally at 34 (Figure 3) aresupported as .a unit from plate 32 which is secured in an .outturnefdflange 35 around the top oithe boiler shell by cap screws 36.

Each of theheating units, of which there are .an'outer circle of eightand an inner circle of ,four, consists of an elongated element havinganouter sheath of. metal, such as a copper tube,

within. which the heating filament is contained, such as a helicallyWoundlength of nichrome insulated fromhthe copper tube by any suitablemeans. ,The heating element is used in the immersed portion of theheating unit, the remainder of the length of the unit being inactive 1orheating,.but containing the lead inwires for switched into and out ofcircuit as a unit. Au-

tomatically controlled operating means forthe -heatingunits willbe'later described. The heat- 'ing elements are arranged inthree phasedelta connection.

. For convenience in lifting out the plate 32 with the heating elementsattached thereto, I provide acentralbossB provided with a threaded hole.into which the lifting hook 'LH shown in Figure 5 may be screwed, and Imay insert a corrosion rod to reduce electrolytic corrosion fitted witha threaded sleeve intothe hole, if desirable,.removing the rod, ofcoursey-before fitting the "hook in place. 'If a corrosion rod is notpositioned in the hole in "boss B during the op-- eration of thegenerator, the hole is closed by a removable threaded plug.

Water from the pump I 4 enters the boiler shell through supply pipe 43.A pipe 44 is connected to the bottom of the boiler shell and is fittedwithablow-down valve .45, enabling the 4 boiler to be cleared ofsediment accumulating in the bottom.

It will be noted from Figure 3 that the heating units 34 are suspendedwell above the bottom of the boiler shell out of the area of sedimentdeposit.

The boiler shell is mounted within a compartment 46 lined with slabs ofinsulating material 41, a dead air space 48, being provided between thesurface 'ofthe insulation andSthe outer surface of the boiler shell,which is effective in reducing corrosion of the latter.

A relatively narrow compartment 48' is providedbetween the front wall ofthe boiler compartment and the front wall of the casing l0 and :a number10f, electrical controls are mounted therein. The front wall of thecasing is provided with a door 49 giving access to the con- .trols incompartment 48.

The top of the casing I0 is formed as a cap or. cover 50 held inposition by sheet v,metal screws 5|, the slabs of insulationapplied tothe cover, over the boiler compartment, being secured theretoybyfastening means 52. 'By. removing screws 5|, the cover maybe'lifted ofiexposing the boiler shell for inspection and-the heating units forremoval. It will. be noted that when plate32 closing the boiler shellis'removed, the interior of the latter may be inspected.

Various control "devices .are mounted on the right-hand side of-thecasing I 0, as seen in Figure3, and are shown in-Figure 2. Furthercontrol devices are mounted on thebackofthecasdevices within the casingof the generator-if desi e The devices mounted on the right-hand side ofthe casing comprise a vertical vessel 53 (Figures Zand 3) connected byapipe 54 to the lower level at which water is maintained in the boilershell during normal functioning of the steam generator and by; a. pipe55 with the boiler shell at the upper limit of, the water level therein.Vessel53 therefore contains a column of water, the surface of which isat the same level as thewater in the boiler, between the predeterminedupper and lower limits. The material of which vessel 53 is made is nonmagnetic, as for instance, brass. Within the vessel, a float 56 made ofmagnetic material is arranged which freely ises and falls withthe levelof the liquid the vessel. .A pipe fittedwith blow-down valve 5.1. .5.connected to the bo tom of ve l 5 and ena es it to be cleanedi utfromtime to time. i

A pipe 58 is connected to the .top of vessel 53 and transmits thepressure in the boiler to pressure operatedelectrical switches 59, 60(Figure 2) arranged in control compartment 48", the function of whichwill be later describedand to a pressure gauge 6 I. A water level gauge62 is connected across. the top and bottom of vessel 53 and is providedwith a blow-down tube 63 connected through gauge blow-down valve 64 withthe blow-down pipe from vessel 53 beyond its blow-down valve 51. Securedto the vessel'53 by straps 65 is a switch box 65 in which are mounted alow water level switch and a high water level switch which switches areof similar. construction and are operated automatically by the positionof float 56 as will be described when later explaining the electricalcontrols of the steam generator. Electrical wirins. between-switchbox 66and theelecirical components mounted in the control compartment iscarried within electrical conduit 61.

Steam is led from the steam space in the upper portion of the boilershell through pipe 68 and steam valve 69 mounted at the back of thesteam generator casing (Figures 2 and 4).

A pipe 19 connected to the steam space of the boiler shell also projectsthrough the back of the generator casing and is fitted with athermostatic vacuum and air release valve H, which closes at apredetermined temperature but is open at lower temperatures and admitsair to the boiler shell thus preventing lower than atmospheric pressuresfrom being set up in the boiler shell when the generator is not inoperation.

Pipe is also fitted with a safety valve 12 to relieve steam pressures inthe boiler shell in excess of a predetermined value. Any steam passinginto valves H and I2 is returned by pipe 13 in which the steam condensesto the water storage tank 23.

The electrical control elements and the control circuits are showndiagrammatically in Figure 6 and comprise a start button 14 and stopbutton 15 mounted on the door 49 of the control compartment, 2. redlight 16 which is lit when electrical power is switched on, and twoamber colored lights H and 18 which are lit when the heating units areenergized; these lights being mounted in a row on the front of the steamgenerator casing above door 49. The start and stop buttons are connectedby flexible leads Y established through the high water level switch (notshown) to operate a multipole main (polem'ain) switch. The push buttonsand multipole (pole-main) switch are represented by the manuallyoperated switch 19 shown in Figure 6. Electrical control elements inaddition to the pressure operated switches 59, 60 arranged in thecontrol compartment 48, comprise elements mounted on a control panel 80secured to the front of the boiler shell compartment. The elementsinclude contactors 8|, 82 effective to make and break the circuits ofthe two groups of heatin units g nerally indicated by numeral 34. Thecontactors are operated by solenoids 83, 84, operating when energized toput the contactors in circuit against the resistance of springs 85, 86.The leads of the solenoids pass through the pressure operated switches59 and 60 which are effective to interrupt the solenoid circuits when apredetermined steam pressure has been attained in the steam space of theboiler.

The leads of the contactors after passing through the pressure operatedswitches are connected to the terminals of low water level and highwater level switches 81 and 88, respectively, which are housed in switchbox 66. The construction of both switches is similar, the low waterlevel switch comprising a pivoted bell crank 89, carrying a permanentmagnet 90 on one arm and having its other arm operating as a movablecontact arm between contact 9| to which the leads from the pressureresponsive switches are connected, and a contact 92 connected to asignal bell 93, the vibrator coil of which is connected to a power lineof the circuit. The bell crank 89 is connected to the return line of thethree wire system shown. A tension spring 93 normally holds lever 89against contact 9|.

The high water level switch 88 comprises a pivoted bell crank lever 94carrying a permanent magnet 95 on one arm and having its other armarranged to make and break contact with a contact 96. A tension spring91 normally holds the arm engaged with contact 96. The bell crank "6lever 94 is connected to the return lead 01! the three wire circuit.Bell crank levers 89 andv 94 are rocked about their pivots by themagnetic attraction of their permanent magnets when float 56 is closelyadjacent the magnets.

While I have described a specific form of magnetic high and low waterlevel control switch, it is to be understood that other suitable formsof limit switches may be utilized.

The circuit of the motor I5 is controlled-by a switch 98 closed by asolenoid 99 when energized by a lead from a power lead of the circuit,the solenoid being connected to the terminal 96 of the high water levelswitch. A tension spring I00 acts to open the switch when the solenoid99 is not energized.

Signal lights I! and I8 are placed across the leads to the heatingelements, which in the described embodiment are arranged in two groups,and signal light [6 is placed across the leads of the pump l5.

It will be assumed that the boiler shell 3| has previously been drainedof water for cleaning purposes and that it is desired to again generatesteam, and that the water supply or inlet valve 26V is open.

Push button I4 is depressed, closing main switch 19, signal bell 93 willstart ringing since the float 56 is aligned with the low water levelswitch 89, which will hold the circuit for the contactors open, but thepump will start delivering water to the boiler since the circuit forsolenoid 99 is 88. The level of the water will rise rapidly in theboiler and therefore also in the water column in vessel 53, raisingfloat 56 so that switch 81 assumes a position due to the action ofspring 93 breaking the bell circuit and completing the solenoidcircuits, through contact 9|, oi the contactors 8| and 82, whichthereupon close sending current through the heating units 34. The waterlevel continues to rise in the boiler, air above the water beingdisplaced through thermostatic valve II and water rises in the watercolumn in vessel 53 until float 56 becomes aligned with high water levelswitch 88, causing it to interrupt the circuit of the solenoid 99holdingthe pump switch 98 closed and thereby enables spring I98 to open theswitch which causes stoppage of the pump motor. The heating elementscontinue to raise the temperature of the water until the temperature ofthe water vapor and air in the steam space of the boiler rises to valuesufficient to cause the thermostatic vent valve H to close, after whichsteam is rapidly generated to the predetermined pressure which operatesthe pressure responsive switches 59 and 60 to interrupt the circuits ofthe solenoids holding the contactors closed. The current to the heatingelements is thereby cut off and steam generation suspended momentarilyuntil the pressure falls the few pounds required to enable the pressureresponsive switches to again close and complete the heating circuitthrough elements 34. Because of the delicate and quick actingarrangement described, a loss of ten pounds in pressure is made up inabout six seconds. The very fast steaming characteristic of my steamgeneration is due to the very large heating surface brought into contactwith the small columns of water flowing upwardly with the turns of thehelically wound heater elements.

I merging the high watt density portion of the heating elements coveredby a sheath of suitable material, such as copper, in the water in theboiler, andleading the low watt density portion of the heating elementthrough the steam or vapor-space, I can provide a steam generator ofsimple and compact arrangement since a greater heating surfaceamay beprovided in a smaller boiler than has .hitherto been possible.

Thepush. button 15 when operated will stop the operation of the steamgenerator by opening the mainswitch- 19, thus cutting ofi current to theheating elements and to the pump, leaving whatever water is in theboiler to cool down. As thespressure and temperature in the boiler shellfalls, the thermo-responsive vacuum'release valve 1 I' will; open,admitting air to the boiler and preventing a pressure below atmosphericfrom being set up therein.

While I have described and illustrated a preferred embodiment of myinvention, it is to be understood that various changes and modificationsmay be made therein by those skilled in the art Without departing fromthe scope of the invention as defined by the appended claims.

I claim:

1. An electrically operated steam generator assembly comprising: avertically mounted boiler shell; electrical heater elements suspendedvertically within said boiler shell; a water tank mounted at a lowerlevel than said boiler; an electrically operated pump delivering Waterfrom said tank into the boiler; a vessel of nonmagnetic materialconnected to the water space of the boiler and containing a column ofwater at the same level as the water in said space; a float of magneticmaterial Within said vessel; a low water level switch and a high waterlevel switch spaced vertically therefrom, each of said switches beingmounted closelyadjacent saidvessel and having a pivoted arm; a magnetmounted on each switch arm, the switches being operated by the magneticattraction between said float and magnets when the wa ter level bringsthe float into position adjacent one or'the other of said magnets;contacts operated by said high water level switch when actuated breakthe circuit to said electrically operated pump and contacts operated bythe low water level switch, when actuated to break the circuit 8 to theheater: elements; said switches being nor-.- mally held in closedposition, and'a: controlpanel carrying electrical control meansgoverning the operation of the steamgeneratcr.

2. An electrically operated steam generator, as set forth in claim 1,and in additioncomprising a warning signal operated by the low waterlevel switch when actuated by the float to interrupt the circuit of theheating elements.

3. In an electrically heated steam generator, a chamber member providedwith a removable top plate, the said chamber member adapted to havewater maintained at a certain level therein and a steam portionincludedbetween thetop plateand the water level, electrical heating units withinsaid chamber member, said electrical heating units in each instancecomprising two substan-,

tially parallel straight conducting portions-suspended from the topplate and a helically coiled V suspended from the top plate and'ahelically coiled T tions and the helically coiled portion at the zonewithin the chamber member containing water having an active portion ofhigh watt density and the straight portions in said steam portion of thechamber member being of low watt density.

4. The device as set forth in claim 3 characterized in that: the chambermember is of small water capacity.

' DAVID M. McGINNISL REFERENCES CITED The following references are of.record in the file of this patent:

' v UNITED STATES PATENTS Van Norstrand June 3, 1941

